In blow molding machines of the wheel type, a wheel supports a plurality of circumferentially spaced sets of molds and is generally rotated about a horizontal axis. Plastic tubing is continuously extruded downwardly between the open mold sections and then the molds are closed as they move about an annular path and the portion of the tubing within the molds is blown within the confines of the mold to provide a hollow article which is a container.
In such an arrangement it is essential to be able to provide air to each set of molds at the appropriate time in the rotation of the wheel to provide air to blow the hollow article within the closed mold and to cut off the flow of air after the article has been formed.
Accordingly, among the objectives of the present invention are to provide an apparatus which will effectively control the flow of air to each set of molds; wherein the apparatus incorporates a valve assembly which is individual to each set of molds and is movable with each set of molds; wherein the timing of the opening and closing of the valve assembly can be readily adjusted along the path of the molds; and which can be readily applied and removed for assembly, maintenance and repair.
In accordance with the invention, the apparatus for controlling the application of the air comprises a valve assembly associated with each set of molds on the wheel and comprises a valve which is opened and closed to control the flow of air to the mold. The valve assembly includes a rotatable cam for moving the valve to open and closed positions, a starwheel associated with the cam, and a first actuator mounted at a first position along the path of the wheel for engagement with the starwheel to rotate the cam and open the valve and a second actuator mounted at a second position along the path of the wheel for engagement with the starwheel to rotate the cam and close the valve.